Vojaki in civilisti pred zapornico, kjer je potekala demarkacijska črta. Na hrbtni strani fotografije so navedena še imena: por. Davo Gros in Rudolf Horvatin.
The pathways of dehydration reaction of both calcium atorvastatin trihydrate (CAT) and grinded CAT were investigated using CRTA technique under controlled residual water vapor pressure of 5 hPa using ...complementary analysis techniques, namely TG, DSC and XRD. The results show that the studied sample is a pure atorvastatin in its trihydrated form and that, under CRTA conditions, it dehydrates in three separated steps between 261 and 393 K, each corresponds to the loss of one water molecule. On the other hand, the grinded CAT dehydrates in one step. From the duration of the CRTA experiment and the X-ray diffraction technique, we have showed that the grinding partially dehydrates CAT, to obtain calcium atorvastatin 1.5 H
2
O, while decreasing its crystallinity. Also, examination by X-ray diffraction technique of the CRTA final products of both, CAT and grinded CAT, showed that the anhydrous phase of CAT is crystallized, whereas the one of the grinded CAT is amorphous. The apparent activation energies corresponding to the dehydration steps of intact CAT (39 kJ mol
−1
and 34 kJ mol
−1
) and grinded CAT (126 kJ mol
−1
and 289 kJ mol
−1
) were obtained by means of two CRTA curves realized at two different reaction rates without any hypothesis on the kinetic model of the reaction.
A simple and precise linear integral method to evaluate the activation energy dependence on the extent of conversion has been proposed. The method leads to consistent results with those from ...differential and integral non-linear procedure (Vyazovkin method). Moreover, the new procedure yields the pre-exponential factor and the kinetic model. The method was evaluated from isothermal, non-isothermal and non-linear non-isothermal data (CRTA).
Over the past 2 decades, there has been active research into the hunt for innovative thermoelectric materials with a high value of figure of merit. To investigate the potential of CsK2Sb as a ...thermoelectric material, we analyzed its electrical and thermal transport properties using density functional theory and Boltzmann transport theory. We found that CsK2Sb is a direct band gap material with a band gap of 1.44 eV using the Gaussian-attenuating Perdew–Burke–Ernzerhof functional with spin–orbit coupling. Using electron–phonon Wannier calculations, we computed the electron–phonon lifetimes for electrons and holes, which are leveraged to estimate absolute values of the electronic transport coefficients by solving the Boltzmann transport equation for electrons. At 300 K, we have found that CsK2Sb exhibits a maximum value of power factor of 5.7 mW K–2 m–1 with electron doping, which is comparable to those of well-known thermoelectric materials. By solving the Boltzmann transport equation for phonons, we demonstrate that CsK2Sb has significantly lower phonon group velocity and phonon–phonon lifetimes than other well-known thermoelectric materials, resulting in an ultralow lattice thermal conductivity of 0.25 W m–1 K–1 at 300 K. At 500 K, CsK2Sb showcases an exceptional figure of merit of 4.69 (2.48) with electron (hole) doping, surpassing all other full Heusler alloys. These findings reveal that CsK2Sb is a “phonon glass electron crystal”, a property of an ideal thermoelectric material.
Biosensors have major advantages over chemical or physical analyses with regard to specificity, sensitivity, and portability. Recently, many types of whole-cell bacterial biosensors have been ...developed using recombinant DNA technology. The bacteria are genetically engineered to respond to the presence of chemicals or physiological stresses by synthesizing a reporter protein, such as luciferase, β-galactosidase, or green fluorescent protein. In addition to an overview of conventional biosensors, this minireview discusses a novel type of biosensor using a photosynthetic bacterium as the sensor strain and the crtA gene, which is responsible for carotenoid synthesis, as the reporter. Since bacteria possess a wide variety of stress-response mechanisms, including antioxidation, heat-shock responses, nutrient-starvation, and membrane-damage responses, DNA response elements for several stress-response proteins can be fused with various reporter genes to construct a versatile set of bacterial biosensors for a variety of analytes. Portable biosensors for on-site monitoring have been developed using a freeze-dried biosensing strain, and cell array biosensors have been designed for high-throughput analysis. Moreover, in the future, the use of single-cell biosensors will permit detailed analyses of samples. Signals from such sensors could be detected with digital imaging, epifluorescence microscopy, and/or flow cytometry.
Dynamic and controlled-rate thermogravimetric analyses have been carried out on acid-treated (11 and 5.8 M HCl), high-iron-content kaolinites as potential photocatalysts. The mineral contaminants ...were determined by XRD, while the defect sites of reduced coordination number obtained by surface treatments were identified with
27
Al MAS NMR spectroscopy. Upon heating, water is evolved from the surface-treated samples in three main stages: (1) removal of adsorbed water up to ~ 200 °C, (2) goethite dehydroxylation between 200 and 350 °C and (3) dehydroxylation of the clay in the 300–700 °C temperature range. Identification of water released from the above mass loss steps is difficult due to the significant overlap of steps 2 and 3, as well as to the presence of coordinated water at broken edges and defect sites (–OH
2
+
groups). As a result, the thermal behavior of surface-treated kaolinites should be taken into account both in the preparation of hybrids/composites and in the acid–base characterization of the catalytic surface.
Thermal decomposition mechanisms for cobaltoblödite Na
2
Co(SO
4
)
2
·4H
2
O and cupper–kröhnkite Na
2
Cu(SO
4
)
2
·2H
2
O have been developed using constant rate thermal analysis technique under ...controlled residual water vapor pressure above the sample
P
H
2
O
=
5
hPa
. The apparent activation energy of each dehydration process was measured by means of two CRTA curves without any presumption to the kinetic low. Correlation between structure and thermal behavior was highlighted. It has shown that dehydration of cobaltoblödite mineral occurs in two steps with formation of Na
2
Co(SO
4
)
2
·1.5H
2
O and Na
2
Co(SO
4
)
2
as intermediate and final phases, respectively. The activation energies of both dehydration steps are 167 kJ mol
−1
and 107 kJ mol
−1
, respectively. For cupper–kröhnkite mineral, its dehydration occurs in one step leading to Na
2
Cu(SO
4
)
2
. The corresponding activation energy was found equal to 71 kJ mol
−1
.
The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. Hydrotalcites containing carbonate, vanadate ...and molybdate were prepared by coprecipitation. The resulting materials were characterised by XRD, simultaneous TG–DTG–DTA and controlled rate thermal analysis (CRTA) to determine the stability and thermal decomposition pathway of the synthesised hydrotalcites. For the carbonate intercalated hydrotalcite dehydration takes place in three steps two of which are quasi-isothermal and one non-isothermal. Dehydroxylation and decarbonation occur separately over the 235–330 and 330–370 °C temperature range. A second non-isothermal decarbonation step is observed in the 371–541 °C range. In comparison the mixed carbonate–vanadate and carbonate–molybdate hydrotalcites show two dehydration steps and the dehydroxylation and decarbonation occur simultaneously. The observation of three dehydration steps is used to support the model of water molecules in three structurally distinct environments in the hydrotalcite interlayer. CRTA technology provides a mechanism for the decomposition of hydrotalcites.
The reaction of magnesium minerals such as brucite with CO
2
is important in the sequestration of CO
2
. The study of the thermal stability of hydromagnesite and diagenetically related compounds is ...of fundamental importance to this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO
2
. This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The dynamic thermal analysis of synthetic hydromagnesite proves that dehydration takes place in two steps at 135 and 184°C, dehydroxylation at 412°C and decarbonation at 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145°C, respectively. In the CRTA experiment both water and carbon dioxide are evolved in an isothermal decomposition at 376°C.
CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial nesquehonite structure.
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